Abstract
A pair of degenerate oligodeoxyribonucleotides was used to amplify, by the polymerase chain reaction (PCR), DNA fragments internal to genes encoding d-Ala: d-Ala ligase-related proteins of vancomycin-resistant (Vm R) Enterococcus faecalis V583. Cloning and nucleotide sequencing of the PCR products indicated that fragments of two genes, designated vanB and ddl, were co-amplified. The vanB gene was previously shown to be present in Enterococcus strains expressing VanB-type Vm R [Quintiliani Jr. et al., J. Infect. Dis. 8 (1993) 943–950]. The ddl gene was detected by Southern hybridization in all Vm R and Vm S strains of En. faecalis, but not in representatives of 17 other species of Enterococcus. The vanB and ddl genes were cloned in bacteriophage λ and sequenced. There was extensive similarity (76% aminoacid identity) between the product of vanB and the Vm R protein, VanA. The product of ddl, the d-Ala: d-Ala ligases, DdlA and DdlB, of Escherichia coli and the resistance proteins, VanA and VanB, were more distantly related (32–40% aa identity). After induction of Vm R, En. faecalis V583 synthesized the cell wall precursor, UDP- N-acetylmuramyl-tetrapeptide- d-lactate, indicating that the mechanism of glycopeptide resistance in strains with the VanA and VanB phenotype is similar.
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